Solenoid switch,particularly cryogenic switch

ABSTRACT

In a two-position solenoid switch an armature made of a nonferromagnetic material of good electric conductivity is movable back and forth between two separately energizable spaced coreless coils. The motion of the armature is started by virtue of the interaction between the magnetic field of the energized coil and the magnetic field generated by the eddy-currents induced in said armature by the energized solenoid.

United States Patent 1191 Kruger 1 Feb. 6, 1973 [54] SOLENOID SWITCH, PARTICULARLY CRYOGENIC SWITCH [56) References Cited [75] Inventor: Peter Kruger, Munich, Germany UNITED STATES PATENTS Assigneel Max-Planck-cesellschafl Zur 2,566,221 8/1951 Lovell ..335 224 derung 'der Wissenschaiten e.v., 3,185,913 5/1965 Gray ..335/180 I Gottingen, Germany Primary ExaminerHarold Broome [22] Fllgd' 1972 Attorney-Edwin E. Greigg [2'1] Appl. No.: 229,820

[57] ABSTRACT [30] Foreign Application Priority Data In a two-position solenoid switch an armature made of a non-ferromagnetic material of good electric conduc- Feb.26, 1971 Germany ..P 2109 327.6 tivity is movable back and forth between two Separate ly energizab'le spaced coreless coils. The motion of the [52] U. S. Cl. ..335/177, 335/100, 335/126, armature is Started by virtue of the interaction 335/l3l 335/149 335/224 between the magnetie field of the energized coil and [51] Int. Cl. ..H0lh 51/12 the magnetic field generated by the eddy currems [58] Field of Search ..335/177, 99, 100, 224,225,

duced in said armature by the energized solenoid.

9 Claims, 3 Drawing Figures SOLENOID SWITCH, PARTICULARLY CRYOGENIC SWITCH BACKGROUND OF THE INVENTION This invention relates to a solenoid switch, particularly a cryogenic switch, and is of the type that has two separately excitable coils, an armature which is movable by virtue of the magnetic field generated by the electric current passing through the coils, and at least one pair of electriccontacts controlled by the armature through an actuating member.

Switches having the afore-outlined characteristics have been known as solenoid relays including two separate actuating coils. Generally, the latter are wound on an iron core and the armature is made of a ferromagnetic material.

In some applications, such as plasmo-physical experiments or use in fusion equipment, no components should or can be made of ferromagnetic material since such componentsmay generate undesired forces or field distortions which interfere with the tests conducted.

OBJECT, SUMMARY AND ADVANTAGES or THE INVENTION It is an object of the invention to provide an improved solenoid switch which is free of components made of ferromagnetic material.

Briefly stated, according to the invention, there are provided two axially spaced coaxial coreless coils, one is energized for closing the switch, the other is energized for opening the same. Between the two coils there is movable back and forth an armature made of a nonferromagnetic material of good electric conductivity. The armature is repelled by the energized coil by virtue of the interaction between the magnetic field generated by the current flowing in the energized coil and the magnetic field generated by the eddy-currents induced tional state can be changed by means of a single pulse and, as a further improvement, very simple means may be provided to prevent, with a high degree of safety, an accidental change of its operational state.

The invention will be better-understood as well as further objects and advantages become more apparent from the ensuing detailed specification of a preferred, although exemplary embodiment of the invention taken in conjunction with'the drawing.

' BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic axial sectional view of the solenoid switch according to the invention;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 and FIG. 3 is a view in thedirection of arrow X in FIG. 1 of a contact component of the solenoid switch.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to FIGS. 1 and 2, the switch shown therein includes two axially spaced coaxial coreless coils 10 and an armature 12 which is movable between these two coils and which has an annular disc-like component 12a and a sleeve-like hub 12a by means of which the armature 12 is affixed (for example, keyed at 16) to an operating rod 14. The armature 12 is made of a material which is a good electric conductor but is not ferromagnetic (such as copper). The coils 10 are mounted in a housing 18 which also serves as a support for the operating rod 14. The latter is displaceable along its axis 20 which coincides with the axis of the coils 10. The housing 18 further carries an attachment 22 which supports the terminals 24 for the two coils 10.

The armature l2 rigidly connected with the operat ing rod 14 is biased by means of an over-the-center bistable spring assembly in such a manner as to urge the armature 12 towards that coil 10 to which it is closer. The said spring assembly is formed of a plurality of approximately axially extending leaf springs 26, which at one of their ends, are secured to the rear side of the housing 18 by means of screws 28. At its other, free terminus each leaf spring 26 is connected to the outer end of a swingable rocker arm 30, the inner end of which extends into a groove 32 of a collar 34 affixed to or integral with the operating rod 14.

In the closed position of the switch, the left-hand terminus of the operating rod 14 (as viewed in FIG. 1) urges a movable contact member 36 into engagement with a stationary contact member 38. I

As shown in FIG. 3, the movable contact member 36 includes a strip-like conductor 40 made of a superconductive material which is connected with a leaf spring 42 also forming part of the contact member 36. One end of both components 40 and 42 is securely tightened to a stationary part 45 by bolts (not shown) passing through screw holes 44. The free end of components 40,42 tapers into a point or may have a trapezoidal configuration with edges substantially in registry with one another. The course of the conductor which forms the stationary contact member 38 and the operating rod 14 (which engages the movable contact at its rear side when viewed in FIG. 3), is indicated in broken lines.

The afore-described switch operates in the following When the switchis in its closed position as shown in FIG. 1 and the left-hand coil 10 is energized with a current pulse of sufficient intensity, in the armature 12 eddy-currents are induced, the magnetic field of which is opposed to the magnetic field induced in the lastnamed coil. Consequently, the armature 12 is repelled by this coil and thus moves towards the right with the operating rod 14, overcoming the force of the springs 26. As the rocker arms 30 pass over the dead center, the springs 26 cause the operating rod 14 to snap towards the right. Thus, the terminus of the operating rod 14 is lifted off the movable contact member 36 which, under the action of the spring force of the leaf spring 42, moves away from the stationary contact member 38 and assumes its open position shown in dashed lines in FIG. 1. The switch is now securely maintainedv in its open position by means of the spring assembly 26, 30. 1

When the switch is to be closed, the right-hand coil 10 receives an electric pulse of sufficient magnitude. Upon this occurrence, the armature 12 is now repelled by the right-hand coil 10 and snaps,'together with the operating rod 14, towards the left into its position shown in FIG. 1 in which it is securely'maintained by the springs 26. It is expedient to design the switch in such a manner that the armature, in the closed position of the switch, does not contact the left hand coil 10 and thus the spring assembly 26, 30 is capable of exerting its full force for maintaining the contact pressure required for a good electric contact.

Since the movable contact member 36 tapers towards its fee end which is also in engagement with the operator rod 14 see FIG. 3), a very good, secure and large area electric contact is ensured. As it may be observed in FIGS. 1 and 3, the operating rod 14 engages the spring 42 at a certain distance from the point of the conductor strip 40 and spring 42. t

In the description that follows there will be set forth a practical embodiment of the invention, including indications of dimensions.

The coils 10 are made of an anodized aluminum strip of 30 turns each. For operating this switch, an electric pulse of approximately 120 Ws is required which may be generated by discharging an appropriate condenser. The natural frequency of the relatively strongly dampened discharge circuit may have a value of, for example, several kHz. In this practical embodiment, the spring 42 is made of a brass sheet 0.5 mm thick, 50 mm long, and 8 mm wide at its secured end. The conductor strip 40 soldered to the spring 42 and the stationary contact member 38 have a width of mm and are made of Nb Sn. The maximum force which the spring assembly exerts with the springs 26 through the operating rod 14 to the movable contact member 36 is approximately 4 kp. The work faces of the contact members may be provided with a very thin coating of a normally conducting ductile metal, particularly tin and copper. In case of a contact closing force of 4 kp, there was measured for the contact assembly shown, at a temperature of liquid helium a contact resistance of approximately 4 X ohm.

It is to be understood that the invention may be practiced with other embodiments. Thus, for example, the

non-ferromagnetic armature may have a form different from that described and may be held in a different manner (for example, it may be pivotally attached). Also, for the coupling of the armature with the movable contact member or contact membersthere may be used other operating members, such as lever arrangements, or any other means. The spring arrangement which determines the two positions of rest of the armature may be formed in a different manner. Thus, the

operating member may be an insulating, knife-like ized as a vacuum switch at a temperature of liquid helium. For this purpose the switch is preferably built into a closed metallic housing which, in operation, may be submerged in liquid helium. The components 36 and 38 which are formed as superconductors as well as the leads to the coils 10 extend in a vacuum-tight isolating conduit. In the switching chamber formed by the housing there may be obtained a very good vacuum by filling the housing at room temperatures with a gas (such as CO condensated at the temperature of liquid helium. The gas then freezes in operation at the temperature of liquid helium and, as a result, a high vacuum is obtained in the housing.

To operate the switch in a vacuum has the advantage that the deionizing periods of the spark during the opening of the switch under load are extremely small.

What is claimed is:

1. A solenoid switch comprising A. two axially spaced, separately energized coreless coils disposed in axial alignment with respect to one another,

B. an armature made of a non-ferromagnetic material having a good electrical conductivity, said arm ature being disposed between said coils for movement back and forth therebetween substantially in the direction of the axis of said coils,

C. an operating member connected to said armature to follow the movements thereof and D. at least one pair of electric contact members operatively connected with said operating member for establishing and breaking an electric contact dependent upon the position of said armature.

2. A solenoid switch as defined in claim 1, said armature including a disc-shaped portion, said operating member including an operating rod extending coaxially with said coils and movable in the direction of their axis, said armature being affixed to said operating rod.

3. A solenoid switch as defined in claim 1, including a bistable spring means at least indirectly connected to said annature for urging the latter towards that one of said two coils which is closer to said armature.

4. A solenoid switch as defined in claim 1, including A. an operating rod, constituting said operating member, extending coaxially with said coils and movable in the direction of their axis, said armature being affixed to said operating rod and B. a bistable spring means for urging said armature towards that one of said two coils which is closer to said armature, said bistable spring means having 1. at least one spring,

2. a rocker arm having a first end swingably connected at least indirectly to said operating rod and a second end connected to said spring urging said rocker arm approximately radially against said operating rod, the force of said spring having an axial component, the direction of which is reversed upon an over-the-center movement of said rocker arm.

5. A solenoid switch as defined in claim 4, wherein said spring is a leaf spring having one fixed end and one movable end, said movable end being connected to said second end of said rocker am.

6. A solenoid switch as defined in claim 4, wherein said springs are two in number and are arranged at diametrically opposite locations with respect to said operating rod.

7. A solenoid switch as defined in claim 1, wherein said at least one pair of electric contact members ineludes A. a movable contact member having '5 6 l. a movable contact strip provided with a fixed end cooperating with that face portion of said movable and a movableend, the terminal portion of said contact member that extends in the range of said last-named movable end being tapered, said lasttapered terminal portion. named portion being in engagement with said 8. A solenoid switch as defined in claim 7, wherein operating b said movable contact strip and said contact face of said 2. a leaf spring coextensive with said movable con- Stationary Contact member is made of a Superconductact strip and being attached thereto at the fixed five material end th f Said l f spring having edges in A solenoid switch as defined in claim 7, wherein gisu-y with the Outlineof the tapered portion of said leaf spring is wider at its location of attachment said movable Contact Strip and I 10 than the width of said movable contact strip. B. a stationary contact member having a contact face v t 

1. A solenoid switch comprising A. two axially spaced, separately energized coreless coils disposed in axial alignment with respect to one another, B. an armature made of a non-ferromagnetic material having a good electrical conductivity, said armature being disposed between said coils for movement back and forth therebetween substantially in the direction of the axis of said coils, C. an operating member connected to said armature to follow the movements thereof and D. at least one pair of electric contact members operatively connected with said operating member for establishing and breaking an electric contact dependent upon the position of said armature.
 1. at least one spring,
 1. A solenoid switch comprising A. two axially spaced, separately energized coreless coils disposed in axial alignment with respect to one another, B. an armature made of a non-ferromagnetic material having a good electrical conductivity, said armature being disposed between said coils for movement back and forth therebetween substantially in the direction of the axis of said coils, C. an operating member connected to said armature to follow the movements thereof and D. at least one pair of electric contact members operatively connected with said operating member for establishing and breaking an electric contact dependent upon the position of said armature.
 1. a movable contact strip provided with a fixed end and a movable end, the terminal portion of said last-named movable end being tapered, said last-named portion being in engagement with said operating member,
 2. a leaf spring coextensive with said movable contact strip and being attached thereto at the fixed end thereof, said leaf spring having edges in registry with the outline of the tapered portion of said movable contact strip and B. a stationary contact member having a contact face cooperating with that face portion of said movable contact member that extends in the range of said tapered terminal portion.
 2. a rocker arm having a first end swingably connected at least indirectly to said operating rod and a second end connected to said spring urging said rocker arm approximately radially against said operating rod, the force of said spring having an axial component, the direction of which is reversed upon an over-the-center movement of said rocker arm.
 2. A solenoid switch as defined in claim 1, said armature including a disc-shaped portion, said operating memBer including an operating rod extending coaxially with said coils and movable in the direction of their axis, said armature being affixed to said operating rod.
 3. A solenoid switch as defined in claim 1, including a bistable spring means at least indirectly connected to said armature for urging the latter towards that one of said two coils which is closer to said armature.
 4. A solenoid switch as defined in claim 1, including A. an operating rod, constituting said operating member, extending coaxially with said coils and movable in the direction of their axis, said armature being affixed to said operating rod and B. a bistable spring means for urging said armature towards that one of said two coils which is closer to said armature, said bistable spring means having
 5. A solenoid switch as defined in claim 4, wherein said spring is a leaf spring having one fixed end and one movable end, said movable end being connected to said second end of said rocker arm.
 6. A solenoid switch as defined in claim 4, wherein said springs are two in number and are arranged at diametrically opposite locations with respect to said operating rod.
 7. A solenoid switch as defined in claim 1, wherein said at least one pair of electric contact members includes A. a movable contact member having
 8. A solenoid switch as defined in claim 7, wherein said movable contact strip and said contact face of said stationary contact member is made of a superconductive material. 